if you can only have 2 gig of ram on the 8 way then i think your decision is made as that would not be beneficial at all.
as far as drives go…
on any mac pro i would run a raid, but..
if your work consists of mainly animating stills, vs if you are doing multi layer comps of HD footage, then those are 2 extremes as far as how disk speed will affect your render time. When you multiply that by 8 cores trying to get that data you can see what type of bottleneck storage becomes.
who is that masked man…